Cholera epidemic
London 1854 John Snow
* Could not provide conclusive evidence that the water was contaminated
* used a map to show that cases centered around the Broad Street pump
* Data showed to the authorities and the pump handle was removed
* A cesspool was leaking i
Nightingale's Legacy
Hospital design
* Fresh air
* Clean drains
* Separate wings
Hospital Management
* Keep no patient in hospital a day longer than necessary
* The very first requirement in a Hospital is that it should do the sick no harm
Public health
* Use of statistics
*
Father of Infection Control
Ignaz Semmelweis
* Mothers died of puerperal fever (child bed fever) which
is caused by Strep. pyogenes
* He required medical students to wash their hands in
chlorinated lime water
* Mortality dropped from 18.3% to 1.3%
* 'savior of mothers'
* Gathered da
Etiologic or causative agent
cause of infection and disease
Koch's postulates
* series of proofs that are the standard for determining the cause of infectious disease
* continue to play an essential role in modern epidemiology
* reliable for many diseases, but cannot be completely fulfilled in certain situations
--Agent can not be
Koch's Postulates
1. Find evidence of a particular microbe in every case of a
disease
2. Isolate that microbe from an infected subject and cultivate it in pure culture in the laboratory; perform microscopic and biological characterization
3. Inoculate a susceptible healthy
Public Health
* The science of protecting and improving the health of
communities through:
--education
--promotion of healthy lifestyles
--research for disease and injury prevention.
* Professionals analyze the effect of genetics, personal choice, and the environment o
epidemiology
* characterized as the basic science of public
health
* the study of the frequency and distribution of
disease and other health-related factors in defined populations
* Involves many disciplines, including microbiology
Techniques of this field used to tra
Centers for Disease Control and Prevention
CDC
CDC
US federal agency under the Department of Health and Human Services
� Protects public health and safety by providing information to enhance health decisions.
� Promotes health through partnerships with state health departments and other organizations.
� P
Reportable or notifiable diseases
� certain diseases must be reported to authorities
� other diseases are reported on a voluntary basis
Prevalence
Epidemiological Statistics: Frequency of Cases
total number of existing cases with respect to the entire population reported as the percentage of the population having a particular disease at a given time
Incidence rate
Epidemiological Statistics: Frequency of Cases
measures the number of new cases over a certain time period
--also called the case or morbidity rate; indicates both the rate and risk of infection
sex, race, or geographical region
Statistics of concern to the epidemiologist are rates of disease with regard to ___, ___ or ___ ___
Mortality rate
measures the total number of deaths in a population due to a certain disease
Morbidity rate
total number of people with a disease in a population
Point-source epidemic
infectious agent came from a single source, and all of its "victims" were exposed to it from that source
� food illness
Common-source epidemic
result from common exposure to a single source of infection over a period of time
� Water plant
Propagated epidemic
results from an infectious agent that is communicable from person to person and is sustained over time in a population
� Influenza
Index case
first patient found in an epidemiological investigation
--first case that brought epidemic to attention of officials
Endemic
cases are concentrated in one area at relatively stable rate
Sporadic
a few cases occur over a wide area
Epidemic
increased number of cases that often appear in geographic clusters; local or nationwide
Pandemic
spread of an epidemic over more than one continent
Presumptive data
place the isolated microbe into a preliminary category
Confirmatory data
pinpoint the microbe's identity
Laboratory Techniques
Specimen collection and analysis
� Collection must use aseptic techniques
� Proper collection, transport, and storage
� Labeling and identifying specimens
Analysis
� Direct testing using microscopic, immunologic, or genetic methods
� Cultivation, isolatio
Phenotypic Methods
Immediate Direct Examination of Specimen
Direct observation of fresh or stained specimen can determine presumptive and sometimes confirmatory
microbial characteristics
Stains most often used
�Gram stain
�Acid-fast stain
Biochemical Testing
Ability of bacteria to use nutrients and other substrates
� indirect evidence of enzymes being present
Includes
� catalase - ability to break down hydrogen peroxide
� oxidase test - ability to use oxygen for energy production
Enzyme-mediated metabolic rea
Dichotomous keys
� flowcharts to trace a route of identification by offering pairs of opposing characteristics
� eventually, an endpoint is reached, where the name of a genus or species is identified
Phage typing
Used for typing Salmonella species
Application
� Used when morphological and biochemical tests are insufficient
Principle
� Bacteriophage infection of bacteria is strain-specific and species specific
Procedure
� a lawn of bacterial cells is inoculated ont
Genotypic Methods
DNA Analysis Using Genetic Probes
Principle
� Hybridization
� uses probes: small fragments of single-stranded DNA or RNA
� Probes are complementary to the specific DNA sequence of a particular microbe
Application
� used to identify bacterial species by de
Polymerase Chain Reaction or PCR
Principle
� Amplifies minute quantities of DNA in samples, improving the sensitivity of a test.
Application
� Used in the identification of a wide variety of microorganisms
� HIV testing for virus using in-office PCR
� Used by hospitals to diagnose MRSA i
Immunologic Methods
The quantity or specificity of antibodies can reveal the history of a patient's contact with microorganisms or other antigens
Serology
Immunologic Method
� involves in vitro testing of serum
� based on the principle that antibodies have specificity for antigens
Immune Testing
General Features of ___ ___
� An antibody binds to one specific antigen
� The most effective serological tests have a specificity and sensitivity
Antibody testing requires
� a known antigen or a known antibody
specificity
ability to detect only a certain antibody or antigen
sensitivity
detection of even minute quantities of antibodies or antigens in a specimen
Immune Testing
Clinical Application of ___ ___
Agglutination and Precipitation Reactions
In both reactions, one antigen is interlinked by several antibodies to form insoluble aggregates
Agglutination
antigens are whole cells or organisms such as red blood cells, bacteria, or viruses
� forms visible clumps of cells
Precipitation
antigen is a soluble molecule
� more difficult to visualize because precipitates are easily disrupted in liquid media
Titer
Concentration of antibodies in serum
� Used to diagnose autoimmune disorders and
determine past exposure to certain diseases
� is determined by serially diluting patient serum into test tubes or wells of a micro-___ plate containing equal amounts of bacte
Serotyping
Ag-Ab technique for identifying, classifying, and sub-grouping certain bacteria into categories
Uses antisera against cell antigens like:
� capsule
� flagellum
� cell wall
� Used in identifying Salmonella species and strains
� Basis for differentiating pn
Immunoassays
� Alternative methods that employ monoclonal antibodies
� Enable rapid, accurate measurement of trace antigen, or antibody levels
ELISA
� uses an enzyme-linked indicator antibody to visualize Ag-Ab reactions
� relies on a solid support such as a micro-titer plate
� The plate either has a known antibody or an antigen absorbed to it.
� The indicator antibody then binds to the antibody antig
Enzyme Linked Immunosorbent Assay
ELISA
Infectious Disease
disruption of a tissue or organ caused by microbes or their products
Infection
entry, establishment, and multiplication of pathogenic organisms
---Begins with contact with a pathogen
---Not all contacts lead to infections
Normal (resident) Biota (normal flora)
Human as a Habitat includes bacteria, fungi, protozoa and viruses
Acquiring Resident Microbiota
*Most areas in contact with the environment harbor resident microorganisms
---Colonization begins during and immediately after birth
*Internal organs, tissues and their fluids are microbe-free
*Most microbes that come in contact with the body are destroye
Microbial antagonism
microbes compete for survival in common environment by inhibiting or destroy other microbes
Normal biota
*unlikely to be displaced by incoming microbes
*limit the number of attachment sites
*Create an environment hostile to other microbes
*beneficial to the host's good health
Probiotics
live microbes to prevent, displace or compete with potential pathogens
Prebiotics
nutrients used to promote growth of favorable microbes in the intestines
Pathogen
microbe whose relationship with its host is parasitic and results in infection and disease
---type and severity of infection depends on pathogenicity of the organism and condition of the host
Pathogenicity
organism's potential to cause infection or disease
True pathogens
capable of causing disease in healthy persons with normal immune defenses
Opportunistic pathogens
cause disease when host's defenses are compromised or when they become established in part of the body not natural to them
Virulence
determined by a microbes ability to establish itself in a host and cause damage
Virulence factor
any characteristic or structure of the microbe contributes to its ability to establish itself in the host and cause damage
Portal of entry
route microbes take to enter tissues of the body to initiate infection
� Skin
� Gastrointestinal tract
� Respiratory tract - most common portal for pathogens
� Urogenital tract
Exogenous
microbe originating from a source outside the body, from the environment or another person or animal
Endogenous
microbe already existing on or in the body, normal biota or previously silent infection
Infectious dose (ID)
minimum number of microbes necessary to cause an infection
single, thousand, billion
microorganisms with smaller infectious doses have greater virulence (spell out numbers)
� ID for rickettsia is a ___ cell
� ID for gonorrhea is a ___ cells
� ID for cholera is a ___ cells
Adhesion mechanisms
� fimbriae
� surface proteins
� adhesive slimes or capsules
� viruses attach by specialized receptors
� parasitic worms fastened by suckers, hooks, and barbs
normal biota
Microbes that encounter the host immune defenses when first entering are not
Phagocytes
cells that engulf and destroy host pathogens by means of enzymes and antimicrobial chemicals
Anti-phagocytic factors
virulence factors that help pathogens avoid phagocytes
� leukocidins: kill phagocytes outright
� slime or capsule: makes it difficult for the phagocyte to engulf the pathogen
� survival inside the phagocyte
leukocidins
kill phagocytes outright
slime or capsule
makes it difficult for the phagocyte to engulf the pathogen
Virulence factors
adaptations a microbe uses to invade and establish itself in a host
3 ways microorganisms cause damage to their host
*directly through the action of enzymes
*directly through the action of toxins (both endotoxins and exotoxins)
*indirectly by inducing the host's defenses to respond inappropriately
Exoenzymes
*Enzymes secreted by microbes that break down tissues
*Dissolve host's defense barriers to promote spread of disease to other tissues
Examples:
---hyaluronidase: digests hyaluronic acid that cements animal cells together
---coagulase: causes cloning of bl
hyaluronidase
Exoenzyme that digests hyaluronic acid that cements animal cells together
coagulase
Exoenzyme that causes cloning of blood or plasma
kinase
Exoenzyme that dissolves fibrin clots
Streptokinase
Exoenzyme that is produced by Streptococcus species
Toxin
specific chemical product of microbes, plants, and some animals that is poisonous to other organisms
---named according to their target
neurotoxins
act on the nervous system
enterotoxins
act on the intestines
hemotoxins
lyse red blood cells
nephrotoxins
damage the kidneys
Exotoxins
proteins secreted by a pathogenic microbe with a specificity for a target cell and toxic effect
Hemolysins
a class of exotoxin that disrupts the membrane of red blood cells to release hemoglobin
---Streptococcus pyogenes produces streptolysins
Endotoxin
lipopolysaccharide (LPS), part of the outer membrane of gram-negative cell walls
---causes fever, inflammation, hemorrhage, and diarrhea
Inducing an Injurious Host Response
More are the result of indirect damage than direct virulence factors, such as enzymes and toxins,
Microbial diseases are the result of
*indirect damage
*excessive or inappropriate immune response
---Superantigens
Localized infection
Pathogens are limited to a small area of the body
---Boils, warts
Systemic infection
An infection that spreads to several sites throughout the body
---Chicken pox, typhoid
Focal infection
Infectious agent spreads from local site to others tissues
---streptococcal pharyngitis
Primary infection
Acute infection that causes the initial illness
Secondary infection
Opportunistic infection after a primary (predisposing) infection
Acute Infection
Symptoms develop rapidly
Chronic Infection
Disease develops slowly
Symptom
Subjective change in body function that is sensed by a patient as a result of disease
Sign
Change in a body that can be objectively measured or observed as a result of disease
Syndrome
Specific group of signs and symptoms that accompany a disease
asymptomatic, subclinical, or inapparent
Infections where
� No noticeable symptoms are produced
� Microbe is present in host tissues
� Host does not seek medical attention
Communicable disease
Disease that is spread from one host to another
Contagious disease
Disease that is easily spread from one host to another
---Chicken pox, measles
Non-communicable disease
Disease that is not transmitted from one host to another
---Tetanus
Direct Transmission
Person to person transmission
*Touching, kissing, sexual contact
*Droplet transmission
---Coughing, sneezing, laughing
*Paterneral
---Injection or contaminated blood
Mechanical vectors
House flies feed on garbage and feces
Biting vector
Transmits a pathogen to a host by biting
*Inject infected saliva into the blood - mosquito
*Defecate around the wound site - flea
*Regurgitate blood into the wound - tsetse fly
Indirect Transmission
Disease transmitted from its reservoir to a susceptible host by means of a non-living object
Fomite
inanimate object that harbors and transmits pathogens
� Doorknobs
� Telephones,
� Faucets, etc
Vehicle Transmission
� Transmission by non-living materials
---Food
---Water
---Air
---Soil
� Fecal oral route
---Vehicles or fomites contaminated with feces
Nosocomial Infections
infections acquired or developed during a hospital stay
--from 0.1 - 20% of all admitted patients, with an avg of 5%
--2 to 4 million cases a year, resulting in 90,000 deaths
--8 million in additional days of hospitalization and an increased cost of $5 to